HVAC Installation Instructions
Installing a new furnace or air-conditioner is not a project for most do-it-yourselfers, but carefully planning and choosing a heating and cooling system is an important part of home improvement or new home construction. With a little bit of research, you can select a system that is just right for your home.
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Choosing a System
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There is no one-size-fits-all, "best" HVAC system; what you should install depends on a number of factors. The first step in selecting the correct heating, ventilation and air-conditioning system (HVAC) for your home is to determine your heating and cooling needs in terms of British thermal units, or BTUs. There is more to determining heating and cooling needs than simply guessing based on a home's square footage. An HVAC contractor does this based on your home's design, volume, air exchange rate and the climate. Once the heat load is calculated, you will know how large of a heater and air-conditioner you will need.
Although fuel costs are obviously variable, it is possible to come up with a good idea of how much your monthly heating bill will be once you know your heat load. The formula involves knowing how many BTUs a particular form of energy provides per unit of measurement and the heating-degree-day data for your area, which indicates the heating energy consumption for an area over time. For example, one kilowatt-hour (kwh) of electricity provides 3,412 BTUs, while 100 cubic-feet (ccf) of natural gas provides 103,000 BTUs. Since you can predict how much a kilowatt-hour of electricity costs vs. a cubic foot of natural gas and how many BTUs you can expect to consume, you can compare different heating and cooling plants to estimate whether a more expensive unit may be more cost-effective in the long run.
If you want to use central air-conditioning, look carefully at a forced-air HVAC system. In a forced-air system, a blower attached to the furnace forces warm air through ducts into a room and pulls cooled air back through return registers to the furnace where it is reheated and recycled. Installing a forced-air system means running a series of galvanized steel ducts behind the walls and atop the ceilings of your home.
Hot water is also used for heating purposes, both as liquid and steam. A hot water system is considered a "closed" system because the same water is used over and over again, circulating through the pipes for years. A steam system is "open" because steam dissipates into the rooms as they are heated. Hot water systems do not have furnaces; instead they use boilers. Hot water systems often require electric-circulating pumps to make sure the heat spreads evenly.
Heat pumps are complex devices that function essentially like reversible air-conditioners, working best in areas where temperatures do not drop below 15 degrees. They take advantage of the principle that liquids tend to absorb heat as they expand into gases and give off heat as they compress. Like air-conditioners and refrigerators, heat pumps require refrigerant chemicals, coils and compressors. They work much like forced air systems with ducts and vents.
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